Effect of hydrogen on carbon formation on Ni/YSZ composites exposed to methane

Nikooyeh, Kasra; Clemmer, Ryan; Alzate-Restrepo, Vanesa; Hill, Josephine M.

doi:10.1016/j.apcata.2008.06.005

Cited by 80 publications

(35 citation statements)

References 22 publications

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“…At the TPB, at which the electrochemical reactions occur, the amount of carbon formed is significantly reduced due to the presence of produced water and/or oxygen ions [100]. Examples of the carbon formed ex-situ and in-situ on Ni/YSZ anodes exposed to methane can be found in references [98,99]. Examples of the different carbon morphologies on various SOFC anodes tested for the direct utilization of EtOH are shown in Figure 9.…”

Section: Kinetics In the Anode Compartmentmentioning

confidence: 99%

“…This problem has been extensively studied for hydrocarbon-reforming processes [93][94][95][96][97]. The morphology of the carbon deposit depends on many factors including temperature, feed [98,99], anodic polarization [100], and type of catalyst used. In particular, different types of carbon may form in the functional and conduction layers of the anode.…”

Section: Kinetics In the Anode Compartmentmentioning

confidence: 99%

“…The reactions in the conduction layer include the reforming and decomposition reactions as described above. The extent of these reactions depends on the operating conditions, anode material [74,91], and the initial gas phase composition [91,99], and determines which species reach the functional layer that contains the TPB. On Ni/YSZ exposed to methane [98], carbon fibers form at temperatures up to ~700 C.…”

Section: Kinetics In the Anode Compartmentmentioning

confidence: 99%

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Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes

2009

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Solid oxide fuel cells (SOFC) have the advantage of being able to operate with fuels other than hydrogen. In particular, liquid fuels are especially attractive for powering portable applications such as small power generators or auxiliary power units, in which case the direct utilization of the fuel would be convenient. Although liquid fuels are easier to handle and transport than hydrogen, their direct use in SOFC can lead to anode deactivation due to carbon formation, especially on traditional nickel/yttria stabilized zirconia (Ni/YSZ) anodes. Significant advances have been made in anodic materials that are resistant to carbon formation but often these materials are less electrochemically active than Ni/YSZ. In this review the challenges of using liquid fuels directly in SOFC, in terms of gas-phase and catalytic reactions within the anode chamber, will be discussed and the alternative anode materials so far investigated will be compared.

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Section: Kinetics In the Anode Compartmentmentioning

confidence: 99%

Section: Kinetics In the Anode Compartmentmentioning

confidence: 99%

Section: Kinetics In the Anode Compartmentmentioning

confidence: 99%

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Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes

2009

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“…In seven further studies , Klein et al 2007, Nikooyeh et al 2008, da Silva et al 2009, Vakouftsi et al 2011, Nematollahi et al 2012, Trabold et al 2012, the same or slightly transformed definitions, as those in Equations (22), (24), and (26), were applied to determine values of the solid carbon activity, a[C k (s)]. The calculations were based on minimization of the Gibbs energy using either commercial software or thermodynamic data from literature.…”

Section: Published Models Of Deposition Equilibriummentioning

confidence: 99%

On thermodynamic equilibrium of carbon deposition from gaseous C-H-O mixtures: updating for nanotubes

Jaworski

Zakrzewska

Pianko‐Oprych

2017

Reviews in Chemical Engineering

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AbstractExtensive literature information on experimental thermodynamic data and theoretical analysis for depositing carbon in various crystallographic forms is examined, and a new three-phase diagram for carbon is proposed. The published methods of quantitative description of gas-solid carbon equilibrium conditions are critically evaluated for filamentous carbon. The standard chemical potential values are accepted only for purified single-walled and multi-walled carbon nanotubes (CNT). Series of C-H-O ternary diagrams are constructed with plots of boundary lines for carbon deposition either as graphite or nanotubes. The lines are computed for nine temperature levels from 200°C to 1000°C and for the total pressure of 1 bar and 10 bar. The diagram for graphite and 1 bar fully conforms to that in (Sasaki K, Teraoka Y. Equilibria in fuel cell gases II. The C-H-O ternary diagrams. J Electrochem Soc 2003b, 150: A885–A888). Allowing for CNTs in carbon deposition leads to significant lowering of the critical carbon content in the reformates in temperatures from 500°C upward with maximum shifting up the deposition boundary O/C values by about 17% and 28%, respectively, at 1 and 10 bar.

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“…The amount and type of carbon accumulated on an anode while utilizing direct hydrocarbons depends on the operating conditions including fuel conditions, temperature, current density, and anode thickness [3][4][5]. The operating conditions including current density, extent of humidification, and temperature can be controlled easily while studying carbon formation on SOFC anodes and good repeatability of these conditions can be achieved between different cell tests.…”

Section: Influence Of Sealingmentioning

confidence: 98%

Influence of Experimental Conditions on Reliability of Carbon Tolerance Studies on Ni/YSZ SOFC Anodes Operated with Methane

et al. 2013

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The effect of experimental parameters on carbon accumulation in the Ni/YSZ anode of SOFC operated at 1,073 K with CH4, has been described in this paper. Experimental parameters including sealing of the cell to the cell holder, operating current, surface coverage by current collector paste on the surface of the anode, and the configuration of the current collector were evaluated in terms of carbon accumulation at the Ni/YSZ anode. The carbon accumulation was quantified using temperature‐programmed oxidation and cells were examined using scanning electron microscopy. The results suggested that variations in any of these experimental parameters could significantly increase or decrease the amount of carbon accumulation on Ni/YSZ anodes, and hence, the reliability of the carbon tolerance studies. In particular, the higher the air leakage rate, the less carbon that accumulated on equivalent anodes. The extent of surface coverage by current collector paste and the configuration of current collector also impacted the amount of carbon accumulation. Less carbon accumulated directly below and near the areas of current collector paste than on the anode areas directly exposed to CH4 and far from the current collector paste. Additionally, variations in the fuel humidity and current levels also significantly influenced the carbon accumulation.

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Effect of hydrogen on carbon formation on Ni/YSZ composites exposed to methane

Cited by 80 publications

References 22 publications

Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes

Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes

On thermodynamic equilibrium of carbon deposition from gaseous C-H-O mixtures: updating for nanotubes

Influence of Experimental Conditions on Reliability of Carbon Tolerance Studies on Ni/YSZ SOFC Anodes Operated with Methane

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